邏輯Stannby無法啟動實時應用的解決思路：

首先需要做的是檢視一下DG環境中的啟動模式，SQL實時應用支援在最高效能和最大可用模式，不支援在最大保護模式的環境中；因為最大保護模式為確保不丟失任何資料，primary上的事務在commit前必須確認REDO已經傳遞到至少一個standby上。

檢視DG的模式：

SQL> set sqlprompt 'PRIMARY > '

PRIMARY > select NAME,DATABASE_ROLE,PROTECTION_MODE,PROTECTION_LEVEL from v$database;

NAME DATABASE_ROLE PROTECTION_MODE PROTECTION_LEVEL

--------- ---------------- -------------------- --------------------

ORCL PRIMARY MAXIMUM AVAILABILITY RESYNCHRONIZATION

當前的為模式MAXIMUM AVAILABILITY（最大可用模式），無需修改，若發現為MAXIMIZE PROTECTION（最大保護模式），需啟動資料庫到mount狀態修改一下資料庫的模式：

PRIMARY > shutdown immediate

Database closed.

Database dismounted.

ORACLE instance shut down.

PRIMARY > startup mount

ORACLE instance started.

Total System Global Area 167772160 bytes

Fixed Size 1218316 bytes

Variable Size 62916852 bytes

Database Buffers 100663296 bytes

Redo Buffers 2973696 bytes

Database mounted.

PRIMARY > alter database set standby database to maximize availability;

Database altered.

最大效能模式對應的是maximize performance

PRIMARY > select NAME,DATABASE_ROLE,PROTECTION_MODE,PROTECTION_LEVEL from v$database;

NAME DATABASE_ROLE PROTECTION_MODE PROTECTION_LEVEL

--------- ---------------- -------------------- --------------------

ORCL PRIMARY MAXIMUM AVAILABILITY UNPROTECTED

PRIMARY > alter database open;

Database altered.

檢視日誌傳輸方式：確保由LGWR傳輸日誌至STANDBY

PRIMARY > select DEST_NAME,STATUS,TYPE,ARCHIVER from v$archive_dest;

DEST_NAME STATUS TYPE ARCHIVER

---------------------------------------- --------- ------- ----------

LOG_ARCHIVE_DEST_1 VALID PUBLIC ARCH

LOG_ARCHIVE_DEST_2 VALID PUBLIC LGWR

LOG_ARCHIVE_DEST_3 INACTIVE PUBLIC ARCH

LOG_ARCHIVE_DEST_4 INACTIVE PUBLIC ARCH

LOG_ARCHIVE_DEST_5 INACTIVE PUBLIC ARCH

LOG_ARCHIVE_DEST_6 INACTIVE PUBLIC ARCH

LOG_ARCHIVE_DEST_7 INACTIVE PUBLIC ARCH

LOG_ARCHIVE_DEST_8 INACTIVE PUBLIC ARCH

LOG_ARCHIVE_DEST_9 INACTIVE PUBLIC ARCH

LOG_ARCHIVE_DEST_10 INACTIVE PUBLIC ARCH

PRIMARY > show parameter archive_dest;

NAME TYPE VALUE

------------------------------------ ----------- ------------------------------

log_archive_dest string

log_archive_dest_1 string location=/u01/log/arch_locatio

n

log_archive_dest_10 string

log_archive_dest_2 string service=orcl_s_tns lgwr valid_

for=(online_logfiles,primary_r

ole) db_unique_name=orcl_std

log_archive_dest_3 string

log_archive_dest_4 string

log_archive_dest_5 string

log_archive_dest_6 string

如發現不是LGWR，而是ARCH傳輸，需修改一下日誌傳輸方式：

SQL> alter system set log_archive_dest_2='service=orcl_s_tns lgwr valid_for=(online_logfiles,primary_role) db_unique_name=orcl_std';

System altered.

細節方便可以根據以下檢視檢視SQL應用資訊：

v$logstdby_state

SQL> select * from v$logstdby_state;

PRIMARY_DBID SESSION_ID REALTIME_APPLY STATE

------------ ---------- -------------------- --------------------

1369377775 1 Y APPLYING

dba_logstdby_events記錄邏輯standby的操作日誌，預設情況下記錄一百條訊息

SQL> desc dba_logstdby_events;

Name Null? Type

----------------------------------------- -------- ----------------------------

EVENT_TIME DATE

EVENT_TIMESTAMP TIMESTAMP(6)

CURRENT_SCN NUMBER

COMMIT_SCN NUMBER

XIDUSN NUMBER

XIDSLT NUMBER

XIDSQN NUMBER

EVENT CLOB

STATUS_CODE NUMBER

STATUS VARCHAR2(2000)

dba_logstdby_log記錄當前重做日誌應用情況

SQL> desc dba_logstdby_log;

Name Null? Type

----------------------------------------- -------- ----------------------------

THREAD# NOT NULL NUMBER

RESETLOGS_CHANGE# NOT NULL NUMBER

RESETLOGS_ID NOT NULL NUMBER

SEQUENCE# NOT NULL NUMBER

FIRST_CHANGE# NOT NULL NUMBER

NEXT_CHANGE# NUMBER

FIRST_TIME DATE

NEXT_TIME DATE

FILE_NAME VARCHAR2(513)

TIMESTAMP DATE

DICT_BEGIN VARCHAR2(3)

DICT_END VARCHAR2(3)

APPLIED VARCHAR2(8)

等等..

溫馨提示：重啟系統後別忘了開監聽…

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